The present invention relates to a method of detecting a lane change of a vehicle having a locating device which uses angular resolution for locating vehicles traveling in front, and a device for determining the yaw rate of the subject vehicle.
Distance- and speed-regulating devices for motor vehicles, also referred to as ACC (adaptive cruise control) systems, are known. In these systems, objects, for example vehicles traveling in front in the same lane as the subject vehicle, are detected using a locating device, for example a radar system which provides angular resolution, which enables the distance and relative speed of the vehicle traveling in front to be measured. The capability for angular resolution in such a radar system has been used in the past to check the detected objects for plausibility, so that, for example, vehicles in the same lane as the subject vehicle may be distinguished from road signs or markings on the edge of the roadway, or from vehicles in other lanes.
When a vehicle traveling in front in the same lane as the subject vehicle is within the locating range of the radar, the traveling speed is regulated by intervention in the drive or braking system of the vehicle in such a way that a speed-dependent distance from the vehicle traveling in front is maintained. On the other hand, if there is no vehicle within locating range in the same lane as the subject vehicle, the device regulates the speed at an intended speed selected by the driver.
German Patent Application 196 37 245 A1 describes an ACC system in which the evaluation of the radar signal for plausibility is modified when the driver indicates his/her intention to change lanes by actuating the left or right turn indicator. In this situation, the travel corridor taken into account in regulating the distance is temporarily extended to the future new lane, and the vehicles in the former lane as well as the vehicles in the future lane are taken into account in regulating the distance. The travel corridor is defined as a strip of fixed, or optionally variable, width on both sides of the prospective travel path of the subject vehicle. For a straight roadway course, the travel path of the subject vehicle is indicated by a straight line running in the direction of travel through the center of the vehicle. For a curved roadway course, it may be assumed as an approximation that the prospective travel path is a curve of constant curvature. Assuming a steady-state curve situation, the particular curvature may be calculated by defining the yaw rate of the subject vehicle via the traveling speed. In principle, the yaw rate may be determined from the steering angle and the traveling speed, but preferably is directly measured using a yaw rate sensor, in particular since such a yaw rate sensor is already present in vehicles having an electronic stability program (ESP).
In non-steady state situations, however, in particular during a lane change, an accurate determination of the travel corridor has proven to be difficult. Merely evaluating the signal from the turn indicator is of no further use here, since actuation of the turn indicator only indicates the intention to change lanes but does not allow the detection of exactly when the lane change starts and ends. Even making additional allowance for the steering commands of the driver does not enable the lane change to be unambiguously detected, since a curved roadway course may also give rise to the steering commands. In the past, these uncertainties in the detection of a lane change have often caused malfunctions in the regulating system due to the fact that during the lane change the radar beam temporarily sweeps over the edge of the roadway and identifies stationary targets such as road signs or the like as presumably relevant objects, or that for roadways having three or more lanes, vehicles in the next-to-adjacent lane are erroneously associated with the travel corridor of the subject vehicle. To accurately associate objects detected using the locating device with the relevant travel corridor of the vehicle, it would therefore be desirable if a lane change could be reliably identified.